Reviving Glass Waste: The Magic of 3D Printing

Charles R. Goulding and Andressa Bonafe sit down and chat with Alex Stiles, co-founder of Vitriform3D.

Despite being infinitely recyclable, only a small fraction of discarded glass in the US is actually given new life. In 2024 alone, an estimated 8 million tons of glass will end up in landfills, where they can take between 4,000 and 1 million years to decompose. We met with Alex Stiles, who is working to change this scenario with the help of 3D printing. The co-founder of Vitriform3D gave us an interesting overview of the challenges of glass recycling and how additive manufacturing can be used to convert low-quality glass waste into the next generation of eco-friendly engineered stone products.

Why is the recycling rate for glass waste in the US only 33% on average? What factors contribute to this?

While working to establish Vitriform3D, I gained considerable insights into glass recycling dynamics in the US. The primary issue is that glass is heavy and its scrap worth is quite low. Unless a city possesses an appropriate processing facility for handling glass, it might just not be economically feasible for them to transport their glass for recycling. Typically, the economic range for shipping is around 150 miles; if the processing facility is beyond this radius, shipping expenses surpass the scrap value.

Though government initiatives like bottle bills can alter these influenced logistics, they generally stay consistent. A case in point is Knoxville, TN. The nearest glass processing facility to Knoxville is in Atlanta, a distance that spans over four hours of drive and is more than 150 miles. This reality is why most of the glass waste generated in Knoxville doesn’t get recycled. Broadly speaking, only one-third of all glass waste across the US is recycled, while around 8 million tons per year, which is two-thirds of the total, just ends up in landfills. This is unfortunate considering glass is robust, durable, and infinitely recyclable.

Conversations with individuals engaged in various recycling ecosystems across the US reveal a recurring pattern: if there is no glass processing center in the vicinity, the city either has to bear the cost (in some cases, quite substantial) of shipping the glass to a recycling plant, or it directly goes to a landfill. Several cities in the US, just like Knoxville, face this predicament. Looking at the traditional recycling method of transforming old bottles into new ones, there are just a few designated glass processing centers across the country equipped for such processing. Since a majority of these are located around large metropolitan regions, the recycling infrastructure often overlooks mid-sized cities and rural communities.

I witnessed this situation personally. When I relocated to Knoxville for my postgraduate studies, the municipality eliminated glass collection from their waste segregation project. A unilateral stream waste pick-up service exists here where all recyclables are thrown into a single bin. The Materials Recovery Facility (MRF) in Knoxville was not equipped to manage glass waste though. As a result, the MRF operator stopped accepting glass, to save its machinery from damages. This step resulted in limiting the options of glass recycling in Knoxville to only a few public drop-off locations, and the collected glass there is transported to Atlanta. As the conclusion of my postgraduation started approaching, I began mulling over the enormous quantity of glass that was becoming landfill waste in my locality, and contemplating how we could repurpose this trash into beneficial, new products. During my time in the graduate program, Dustin Gilmer, who would later become my co-founder and I began conceptualizing, and we discovered that 3D printing could be the answer.

Your learning experience at the University of Tennessee seems pivotal in the establishment of Vitriform3D. Could you provide some more details about your scholastic and occupational journey that contributed to that?

It’s been somewhat of a wandering journey, but my key skills are in mechanical engineering. Mechanical engineering is also my undergraduate major, and post-undergraduate I got associated with the railway industry dealing with product engineering. I was exposed to multiple aspects of product designing, and the necessity to reconcile the sometimes discordant requirements of our ultimate consumers. In the rail industry, the majority of our creations must be robust enough for rough usage.

At times, this requirement is to be taken literally – a product may be employed as a hammer, regardless of whether it’s originally meant for that purpose or not! The significant role that materials have in product designing intrigued me and led me to resume my studies, this time poring over composites in postgraduate school. I already accrued some experience in working with composites during my undergraduate years and even before that, so I enrolled in the University of Tennessee for my doctorate, learning under Dr. Uday Vaidya, a globally recognized authority in advanced composites production.

My deepened understanding of the complex relationship between part design, materials, and manufacturing was greatly enhanced during my time in grad school. There were numerous occasions when our lab would be approached by companies with the intention to transition a metal part to a carbon fiber counterpart, but were unsure of the process. They were eager to develop something that was not only stronger, but also lighter.

In collaboration with other graduates, we walked these companies through a variety of methods they could utilize to create a carbon fiber part, considering part complexity and production volume. We also engaged in prototyping and testing to ensure the final product met their expectations. This experiential learning process was, in my opinion, the optimal graduate school experience I could have chosen. I have always viewed myself more as an applied researcher, rather than a scientist, and this hands-on problem-solving methodology perfectly suits that outlook.

In what ways has this problem-solving mindset influenced the co-founding of Vitriform3D?

The reality is, within the United States, there is a required minimum amount of glass waste in a certain area to allow a traditional glass processing center to be viable. Such centers need to process tens of thousands of tons annually to remain profitable.  Contaminants such as stone and ceramic pose a significant concern for these centers, and the large volumes allow for the investment in specialized automated equipment to handle this issue. While these centers do an excellent job in creating cullet for new bottle production or fiberglass insulation, it also opens up opportunities for technologies capable of utilizing lower volume, lower quality glass supplies.

And that’s where our technology comes in. We can work with lower-quality glass and lower volumes of glass because we use a room-temperature 3D printing process. For us, it doesn’t matter if there’s a little bit of ceramic blended in. If there happens to be a coffee mug that made its way into that glass scrap, it’s fine. We also have flexibility as far as the quantity we take in. Our goal is to be able to build regional factories that can process up to 10,000 tons of glass per year, converting it into 3D-printed engineered stone products.

Could you tell us more about Vitriform3D’s technology and its potential applications?

Most companies that are offering 3D-printed glass target very small, low-volume applications, such as lenses, for instance. That is fantastic work, and some of these companies can even use recycled glass in their process. Where we stand out is that we will produce larger scale, higher volume products because we are using binder jetting as our core technology. This powder-based process is well adapted to work with a wide variety of materials. We’ve already proven that it can work with crushed glass, which is essentially sand.

Crushed glass [Source: Vitriform3D]

Our co-founder Dr. Dustin Gilmer, a binder jetting specialist and I have worked on perfecting a new addition to the technology which involves the combination of binder jet printing with photopolymers. Instead of the usual binders, we have opted for UV-curing polymers. This allows us to streamline the binder jet process leading to parts with complete strength directly from the print bed, bypassing the need for sintering or oven-curing post-processes. Our process offers stone-like strength directly out of the print bed, in competition with or surpassing the strength of conventional cement and engineered stone items.

Further, photopolymers will enable us to utilize more features of inkjet technology, such as full-color printing. UV binder jetting will thus manufacture parts with stone-like properties in a wide range of textures and full-color patterns, or even embedded graphics like logos. This combination of aesthetic appeal and durability is particularly attractive to designers and architects. It’s ideally suited for both internal and external surface applications. Consider, for instance, the fiber cement board used as siding or cladding material on the exterior of a house, or tiles (be it porcelain, ceramic, or cement), intended for internal and external usage – these are the very applications we aim to target.

Additionally, another advantage bestowed by our technology is the substantial reduction in carbon footprint when printing with recycled glass. Embodied carbon in usual cladding materials represents the third-highest source in a typical residence, and traditional building materials contribute to around 11% of global greenhouse gas emissions. By using 95% locally sourced recycled glass, completely eradicating cement, and avoiding kiln firing, we estimate that our 3D printed products will have embodied carbon up to four times less than that of a standard ceramic tile or fiber cement board.

Can you share the current progress on development and testing, the key landmarks achieved so far, and your future vision for Vitriform3D?

At this point, we have reached the prototype stage. Originating as a subsidiary from the University of Tennessee, Knoxville, my business partner, Dr. Dustin Gilmer, and I conceived this idea jointly. Dustin specializes in binder jet technology, which has been his focus during his PhD. I, on the other hand, have a background in composites manufacturing. Our shared knowledge in photopolymer composites and binder jetting led to the creation of Vitriform3D. The technology is being licensed from the University.

The conceptualization started in 2021 and later we collaborated with senior design teams at the University to develop our initial proof-of-concept printer. This printer served as a demonstration model for combining UV curing with glass powder. Further, in 2022, we acquired acceptance into the Innovation Crossroads program of Oak Ridge National Laboratory. Joining this program granted us access to eminent scientists from the field of additive manufacturing and helped our company transition from basic bench-top scale testing to complete prototype capabilities. We owe our advanced prototype printer model, a custom system from B-Jetting, to Innovation Crossroads. This unique equipment will allow us to experiment with binder development and testing various glass powders, color combinations of glass, and even mixing other materials.

Despite being in the research and development phase still, we managed to secure over $1.1 million in funding from the U.S. Department of Energy. This financial backing will support us through to our subsequent printer, a robotic arm-based print system capable of manufacturing 3-ft by 3-ft panels. We anticipate that this pilot scale system will be functional within the upcoming year.

We anticipate launching our first 3D-printed building product line in 2025. In 2024, we plan on raising a seed funding round to help us grow our team and secure a location for commercial production.

Before we conclude, could you tell us more about Fourth & Glass Recycling Co. and how it relates to Vitriform3D?

We are part of the circular economy, and our company is actually two companies in one. We recently launched Fourth & Glass Recycling Co., which is responsible for glass collection and processing to bring in the raw material supply that can then be utilized by Vitriform3D.

Glass waste for recycling [Source: 4th & Glass Recycling Co.]

Originating from similar conditions that brought about the establishment of Vitriform3D, Fourth and Glass came about when glass was removed from kerbside collections. When we commenced technology development, we started bringing more and more glass into our workspace. At that point, we noted a requirement in Knoxville that was yet to be fulfilled. Local households were inclined towards recycling glass, but they also needed the convenience of kerbside programs.

Subsequently, we felt that launching a glass pick-up service for residents was an excellent solution to fulfill this need. Currently, we have 108 households that have enrolled for the collection, as a result, we have already been successfully averting over one ton of glass per month from the landfill. Our ambition is to have 1000 subscriber households.

As we look ahead into the upcoming years, we anticipate that the propagation of this program will contribute substantially to our 3D printing procedures. We foresee a hub in Knoxville equipped with 10 large-scale automated binder jet printers. Combined, they would have the capacity to generate five million square feet of tile or external cladding annually while diverting approximately 10,000 tons of glass from Knoxville’s landfills. Our aspiration following this is to construct factories at a regional scale throughout the nation.

Conclusion

Our conversation with Alex Stiles from Vitriform3D gave us an interesting perspective on how additive manufacturing can help reduce the proportion of glass waste that ends up in landfills across the U.S. Potential applications of 3D-printed, stone-like products in architecture are particularly exciting and add to the vast array of transformative solutions that promise to revolutionize our built environment.

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